US7570042B2 - Method for evaluating the effect of an electric discharge on a composite material - Google Patents

Method for evaluating the effect of an electric discharge on a composite material Download PDF

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Publication number
US7570042B2
US7570042B2 US11/807,902 US80790207A US7570042B2 US 7570042 B2 US7570042 B2 US 7570042B2 US 80790207 A US80790207 A US 80790207A US 7570042 B2 US7570042 B2 US 7570042B2
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Prior art keywords
aircraft structure
electric
effect
electric discharge
mesh
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US11/807,902
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US20080258705A1 (en
Inventor
Valentín García Martínez
José Ignacio López-Reina Torrijos
Raúl Fernández Recio
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Airbus Operations SL
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Airbus Espana SL
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/72—Investigating presence of flaws

Definitions

  • the present invention relates to a method for evaluating the effect of an electric discharge on a composite material through the damage caused due to the effect of thermal heating.
  • the evaluation of the thermal behavior of a material due to a severe electric discharge is required in the event that this material is in contact with areas in which there is a possible risk of ignition, for example and for the aeronautical field, in areas in contact with the fuel of the aircraft and/or with its gases.
  • a prediction of the temperature reached in the material is required for the purpose of being able to prevent hot spots: the high current density in certain spot locations of the structure of the aircraft may cause high temperature spots. If this temperature exceeds 200° C. (ignition point of fuel considered by the FAA/JAA), the fuel may reach its inflammation point if the suitable concentrations are present inside the tank.
  • Structural damage holes, melted material, peeling in the case of composite materials, etc.
  • Structural damage which need to be known in order to prevent the mechanical behavior of the material after the impact, may occur due to thermal effects.
  • the present invention is thus aimed at solving these drawbacks in the case of aircraft structures made of composite material.
  • the present invention proposes a method for evaluating the effect of an electric discharge on an aircraft structure made of composite material through the evaluation of the damage caused due to the effect of the thermal heating generated by the mentioned discharge on the structure.
  • the composite material forming the aircraft structure has physical properties and thermal properties that differ according to the chosen direction of the material. This method can approximately estimate these damages and could therefore drastically reduce the number of tests conducted. It will further allow greater freedom when investigating new designs as well as optimize these new designs and those designs already tested.
  • the method of the invention therefore comprises the steps of:
  • FIG. 1 shows the classification into areas of an aircraft according to the probability thereof of experiencing an impact from an electric discharge.
  • FIG. 2 shows the distribution of the aircraft structure by means of a mesh of resistive electric elements.
  • FIG. 3 shows the thermal behavior of the material of the aircraft structure.
  • the present invention therefore provides a method for evaluating the effect of an electric discharge on an aircraft structure made of composite material through the evaluation of the damage due to the effect of thermal heating caused by the mentioned discharge on the structure.
  • the probability of an aircraft suffering a lightening bolt impact is high, it being calculated that an aircraft experiences on average almost 2 lightening bolt impacts per year. Therefore, it is necessary to take the necessary steps assuring firstly the safety of the passengers, and secondly making this lightening bolt impact have the smallest possible effect on the operation of the aircraft.
  • an aircraft structure is split into different areas from the direct impact point of view, the protection of the outer structure of the aircraft thus depending on what region the part to be protected is located in.
  • An aircraft structure is split into the following regions:
  • the method of the invention thus comprises the following steps described in detail below.
  • the physical phenomenon which is applied on the material of the aircraft structure is that of an electric discharge or lightening bolt.
  • the electric discharge occurs from a focal point which is at a much higher potential than the object on which the discharge falls, which is the object of study.
  • this potential difference exceeds the dielectric capacity of the medium (in this case, air)
  • an electric arc is formed between the focal point and the object, which allows studying the discharge of a lightening bolt (electric arc) from a cloud (focal point) in the field of aeronautics.
  • the electric arc is characterized by certain magnitudes, such as the diameter of the arc, which is obtained from the data obtained by means of tests, the intensity that is transferred, the curvature of the arc, the angle of incidence of the lightening bolt, etc.
  • the arc is considered perpendicular to the material of the aircraft structure under study.
  • the electric discharge is considered to be a function of the current intensity transmitted by this discharge over time
  • the electric discharge is represented by means of a direct current generator, further considering that the current density is constant in the cross section of the electric arc and that the properties of the electric arc do not change over time (stationary electric arc).
  • the material will be split into smaller parts called cells 7 .
  • a resistive contact R will be defined between each of these cells 7 and the adjacent cells.
  • the material of the aircraft structure is therefore modeled as a mesh 8 of resistances R, as can be seen in FIG. 2 . The ends of this mesh are joined so that all of them are at the same potential, simulating the current return.
  • the designed method allows including the performance of several classes of material, “z” referring to the direction of the thickness and defining the “xy” plane as the plane locally perpendicular to the “z” axis; the material has a conductivity which may change according to “z”, i.e. in each “xy” plane there may be a different electric and thermal conductivity.
  • the method of the invention thus allows evaluating composite materials (the electric properties of which change in each layer of the stack), as well as homogenous metallic materials. It also allows introducing layers of other different material. For example, a composite material plus a mesh made of a metallic material on the surface of the composite material, a design that is widely used in the field of aeronautics for protecting structures against electric discharges, can be evaluated.
  • the electric mesh 8 of the material of the aircraft structure is resolved by a standard electric circuit resolution method from the intensity which is introduced in the mentioned mesh 8 by the direct current generators.
  • the method of the invention considers the material of the aircraft structure as anisotropic, i.e. it considers that its thermal properties depend on the direction.
  • the contour conditions of the material are considered adiabatic, except in the interface between the lightening bolt and the test piece, in which the lightening bolt injects heat into the material, the electromagnetic energy which is introduced in the material is concentrated therein, not taking into account the possible energy that the lightening bolt itself is to radiate.
  • the current return is modeled as ground, meaning that the ends of the material are at the same potential, as can be seen in FIG. 2 .
  • thermal energy sources there are two thermal energy sources: the interaction in the interface between the electric arc and the material, and the heating of the material due to the Joule effect when the intensity circulates inside it.
  • the energy transferred to the material will be enough to cause a change of state.
  • the change of state is shown in FIG. 3 .
  • the cell 7 of the electric mesh 8 of the material of the aircraft structure is no longer taken into account for the purpose of transmitting heat, all the energy that the cell 7 had up to that point from the evaporation being transferred to the cell immediately under it.
  • the cells 7 which have been evaporated are obtained and the damaged caused in the material of the aircraft structure can be evaluated.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Pathology (AREA)
  • Biochemistry (AREA)
  • Immunology (AREA)
  • General Physics & Mathematics (AREA)
  • Electrochemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Investigating Or Analyzing Materials Using Thermal Means (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Laminated Bodies (AREA)
US11/807,902 2007-03-30 2007-05-30 Method for evaluating the effect of an electric discharge on a composite material Expired - Fee Related US7570042B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ES200700858A ES2341407B1 (es) 2007-03-30 2007-03-30 Metodo para la evaluacion del efecto de una descarga electrica sobre un material compuesto.
ES200700858 2007-03-30

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US20080258705A1 US20080258705A1 (en) 2008-10-23
US7570042B2 true US7570042B2 (en) 2009-08-04

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US (1) US7570042B2 (pt)
EP (1) EP2137521B1 (pt)
BR (1) BRPI0809991A2 (pt)
CA (1) CA2682673C (pt)
ES (1) ES2341407B1 (pt)
WO (1) WO2008119665A1 (pt)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120091269A1 (en) * 2010-10-13 2012-04-19 Airbus Operations, S.L. Lightning strike protection in aircraft

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114676508B (zh) * 2022-05-26 2022-08-16 中国飞机强度研究所 大梯度快时变极端高温环境空天飞机结构热强度评估方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2386647A (en) * 1941-02-24 1945-10-09 Gilbert J C Andresen Method and apparatus for detecting and neutralizing static charges on aircraft or the like
US4323946A (en) * 1979-09-20 1982-04-06 Traux Robert L Apparatus for reducing electrostatic charge storage and EMI on dielectric surfaces
US4531691A (en) * 1980-07-03 1985-07-30 Office National D'etudes Et De Recherche Aerospatiales (Onera) Method and means for protecting an aircraft against disturbances of electrostatic origin
US6900642B2 (en) * 2001-09-28 2005-05-31 Bae Systems Information And Electronic Systems Integration Inc Aircraft electrostatic discharge test system

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4156182A (en) * 1976-09-13 1979-05-22 The Boeing Company Lightning strike detector

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2386647A (en) * 1941-02-24 1945-10-09 Gilbert J C Andresen Method and apparatus for detecting and neutralizing static charges on aircraft or the like
US4323946A (en) * 1979-09-20 1982-04-06 Traux Robert L Apparatus for reducing electrostatic charge storage and EMI on dielectric surfaces
US4531691A (en) * 1980-07-03 1985-07-30 Office National D'etudes Et De Recherche Aerospatiales (Onera) Method and means for protecting an aircraft against disturbances of electrostatic origin
US6900642B2 (en) * 2001-09-28 2005-05-31 Bae Systems Information And Electronic Systems Integration Inc Aircraft electrostatic discharge test system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120091269A1 (en) * 2010-10-13 2012-04-19 Airbus Operations, S.L. Lightning strike protection in aircraft

Also Published As

Publication number Publication date
EP2137521B1 (en) 2014-06-04
US20080258705A1 (en) 2008-10-23
CA2682673A1 (en) 2008-10-09
EP2137521A1 (en) 2009-12-30
ES2341407A1 (es) 2010-06-18
BRPI0809991A2 (pt) 2014-10-14
CA2682673C (en) 2016-05-24
ES2341407B1 (es) 2011-06-13
WO2008119665A1 (en) 2008-10-09

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